Cast heat exchanger tube assembly



' Sept. 29, 1964 H. JACOBS ETAL I 3,150,714

CAST HEAT EXCHANGER TUBE ASSEMBLY Original Filed Sept. 1,1955

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United States Patent 3,150,714 CAST IHEAT EXCHANGER TUBE ASSEMBLY Heinz Jacobs, Geldern, and Johannes Claesgens and Friedhert Heyn, Krefeld, Germany, assignors to Indnstrie-Companie Kleinewefers Konstruktionsund Handelsgeseilschaft m.h.H., Krefeld, Germany, a corporation of Germany Original application Sept. 1, 1955, Ser. No. 533,170, now Patent No. 3,039,744, dated June 19, 1962. Divided and this application Feb. 15, 1962, Ser. No. 173,584

16 Claims. (Cl. 165134) This invention is a division of our application Serial No. 553,170, filed September 1, 1955, now Patent No. 3,039,744 granted June 19, 1962.

The present invention relates to improvements in or relating to heat exchangers, and is more particularly concerned with cast heat exchanger tubes and heat exchangers assembled from such tubes.

Cast heat exchanger tubes have the advantage, as compared with steel tubes, that they are resistant to corrosion and to short time excess temperatures, and that a large heating surface and consequently a high heat output can be provided with a small space. On the other hand, steel tubes have the advantage, as compared with cast heat eX- changer tubes, that they can be welded Without special preparations. The connection of the individual tubes to form parallel flow tube blocks is facilitated considerably by welding, which also insures a nearly perfect fluid seal that is not possible to obtain to a similar perfection in the case of cast heat exchanger tubes, which have hitherto required screw connections.

The object of the invention is to combine the advantages of cast tubes with those of steel tubes.

The invention consists in the provision of a cast metal tube for use in a heat exchanger, said cast tube having a steel tube in the wall of at least one end thereof and prolongation of the cast tube wherein the end portion of the steel tube is fixed in the cast tube by casting the tube in such a way that said portion of the steel tube is embedded in the adjacent end of the cast tube.

The cast-in steel or preformed steel tube ends projecting from the cast tubes render possible the welding of the latter so that the cast heat exchanger tubes practically can be welded together to form parallel flow tube blocks in the manner hitherto possible only with steel tubes.

A tight and durable connection between the steel tube and the cast tube is essential. For this reason it is advantageous if that end of the steel tube which is to be cast in is sharpened in the manner of a knife edge. The steel becomes reliably fused to the cast iron at the knife edge, thus formed, so that the union is and remains fluidtight. Alternatively, that part of the steel tube which is cast in may be profiled so as to increase its surface. In addition, recesses may be formed in the cast-in part of the steel tube sections.

According to a further development, there are provided near to the ends of the exchanger tube supporting and screening flanges made in one piece with the cast tube. The said flanges protect the cast-in steel tube sections at the ends of the cast tubes and the welding joints thereof from overheating by the heat emitting gases which wash the tubes between the screening flanges.

In accordance with our invention, a gate in the upper section of a mold is so located that during the casting of the cast metal tube, it is right above one end of the preformed steel tube which is to be joined to the cast metal tube. The poured stream of molten metal engages the end of the preformed tube and heats it, thus permitting use of the preformed tube in the mold without preheating it. Accordingly, the molten stream of cast metal heats it sufiiciently to effect a good welding connection between Patented Sept. 29, 1 964 "ice the preformed steel tube or section and the cast metal tube or section and to produce a fluid-tight tube.

Instead of the preformed steel tube ends being welded to tube plates in the assembly of the tubes to form heat exchangers, the preformed steel tubes have at their outer ends polygonal flanges, the edges of which are welded to the edges of the flanges of adjacent tubes, so that the flanges themselves form the tube plate. It is further advantageous to bend over outwardly the edges of these flanges with the result that the edges of said flanges abut at an acute angle and render possible the welding of the edges by the simple melting down method. When it is desired to replace a tube in the tube block or network, it can readily be detached from the tube block by grinding ofl the welding seam of the flanges of the tube concerned.

The elastic yielding connection of the tubes may be further improved by forming one or more constrictions between the flange and the cast in end of the preformed steel tube, so that the preformed steel tube acts in the manner of a corrugated tube compensator. Such a steel tube having a flange and constrictions is advantageously assembled from two or more welded portions, the welding seams being placed at the narrowest points of the constrictions.

In the accompanying drawings, we have shown preferred embodiments of our invention in which:

FIGURE 1 is a partial side elevation view in section of a heat exchanger which has a first embodiment of our invention;

FIGURE 2 is a view along the line 11-11 of FIGURE 1;

FIGURE 3 is a section view similar to FIGURE 1 showing a second embodiment of our invention; and

FIGURE 4 is a section view similar to FIGURE 1 showing a third embodiment of our invention; and FIG- URE 5 is an enlarged fragmentary section view of one tube of the heat exchanger of FIGURE 1 showing a joint of a cast metal section and a preformed steel section of the tube.

Referring to FIGURES 1 and 2, a heat exchanger 1 comprises a plurality of tubes 2, 3 and 4 through which flows air to be warmed. Hot waste or exhaust gases travel at substantially right angles across and around the tubes to produce a heating of the air flowing therethrough. As shown, the tubes are in a horizontal position but they may also be arranged in a vertical position.

Each tube comprises a relatively thick walled intermediate section 5 made from cast metal such as iron or steel and a section 6 of preformed steel at each end of the intermediate section. The section of preformed steel is a prolongation of the intermediate section and when connected thereto, forms the tube. This section of preformed steel has relatively thin walls compared to those of the intermediate section and is attached to the intermediate section by placing it in a casting mold in which the intermediate section is to be made. We position the preformed section such that one end 7 thereof has molten metal cast therearound when making the intermediate section 5 to effect a good weld of the preformed section 6 within the intermediate section 5. Upon completion of casting the intermediate section, end 7 of the preformed section extends into and is welded to end 8 of the intermediate section as shown in FIGURE 1. FIGURE 5 shows an area 49 in which the preformed section 6 is fused with the cast metal section 5.

Integral with the intermediate section and adjacent each end is an external collar such as collar 9 of tube which is substantially perpendicular to the central axis of the tube and extends radially a distance to engage and abut a corresponding collar 10 of the adjacent tube 3. In this way, the collars provide support for the tubes and relieve the preformed steel sections of carrying the weight thereof. Additionally, the collars in engagement with one another form a wall at eachend of the intermediate section which protects the preformed sections from the hot waste and exhaust gases, thereby avoiding overheating thereof. FIGURE 1 shows that each collar has a thickness of suflicient amount to provide support for its abutting tubes when some movement of its tube occurs due to expansion and contraction caused by changes in temperature of the hot waste gases in contact therewith.

As shown in FIGURE 1, each preformed section has an outwardly extending flange such as flange 11 of tube 2 disposed radially thereto and projecting an amount sufficient to abut the corresponding flange 12 of the preformed section 13 of adjacent tube 3 at its periphery. The flanges are joined together by welds 14 to form a network of tubes.

FIGURE 3 shows a second embodiment of our invention wherein preformed steel sections 15 and 16 of tubes 17 and 18 respectively have outwardly radially extending flanges 19 and 20 which terminate in forwardly extending lips 21 and 22 disposed substantially parallel to the longitudinal axes of the tubes. The lips 21 and 22 are located radially from the longitudinal axes of their tubes a distance sufficient to abut each other and the flanges 19 and 29 are joined together at the ends of the lips by a weld 23. For convenience in welding the flanges of adjacent tubes, the lips so abut and engage one another that welding of the edges is a melting down process.

In a third embodiment of our invention, each of preformed steel sections 24 and 25 of tubes 26 and 27 (FIG URE 4) comprises a constriction or throat part 28 disposed between their outwardly radially extending flanges 29 and 3t and those ends 31 and 32 of the preformed sections attached to the intermediate sections 33 and 34.

As shown, the preformed sections are made from two parts welded together peripherally at the narrowest part of the constriction. The flanges terminate in forwardly extending lips 35 and 35 positioned substantially parallel to the longitudinal axes of the tubes. Similar to the other two embodiments, the lips are located radially a distance sufficient to abut each other and the flanges 29 and 30 are joined together by welds 37 at the ends of the lips.

The constriction or throat and the flange of both preformed sections 24 and 25 form a convolution and permit expansion and contraction of each tube independently of the other tubes. This is important for each tube has ability to relieve itself of stresses generated by expansion and contraction due to changes in temperature of the hot exhaust or waste gases traversing the exchanger. Additionally, those tubes at the inlet side of the flow of the hot gases through the exchanger encounter different temperatures of gas than those tubes at the outlet side of the flow. As a result, each tube can individually expand and contract independently of the other tubes and thereby avoid production of stresses in the exchanger.

Of course, the preformed sections may have a convolution for expansion and contraction which does not include a constriction and is an outwardly extending radial projection intermediate the flange and the end embedded within the cast metal section.

The heat exchanger tubes of our invention permit easy removal from and replacement in a heat exchanger by severing, grinding off, filing off, etc. the weld or welds between abutting flanges. Thus, the tube whose weld flange has been freed from adjacent flanges is merely pulled out of the network and another tube inserted into its place. The lips on the flanges have an added feature, namely, ability to be rewelded a plurality of times after cutting the welds because there remains suflicient metal of the flange in abutting position with flanges of adjacent tubes for repeated rewelding. In this way, removal and replacement of tubes may occur a number of times without replacing the preformed steel sections.

While we have shown and described preferred embodiments of our invention, it is understood that it may be otherwise embodied within the scope of the following claims.

We claim:

1. A heat exchanger comprising a plurality of elongate tubes, each tube comprising a relatively thick walled section of cast metal with two ends and a section of preformed steel attached to at least one of said two ends of said cast metal section to form said tube, said cast metal section having an external collar adjacent each end which abuts with similar collars of adjacent tubes to form with said collars of said adjacent tubes a wall near each end of said cast metal section to protect said preformed steel section from hot gases of the exchanger, said collars being movable upon one another, said preformed steel section having a substantially outwardly radially extending flange which projects a distance sufficient to abut a corresponding flange of an adjacent tube, said flange being adapted to be joined together along at least a part of its abutting portion.

2. The heat exchanger of claim 1 characterized by said preformed steel section being joined to its cast metal section by a molten metal casting around a part of said preformed steel section which extends into said cast metal section.

3. The heat exchanger of claim 1 characterized by said flange of said preformed steel section extending radially outwardly a distance equal to substantially that distance which said collars extend.

4. The heat exchanger of claim 1 characterized by said flange of said preformed steel section terminating in a lip disposed substantially parallel to the longitudinal axis of its tube.

5. The heat exchanger of claim 1 characterized by said preformed steel section having intermediate its flange and that part joined to said cast metal section a substantially radially disposed constriction for expansion and contraction of said tube.

6. The invention of claim 5 characterized by said flange terminating in a lip disposed substantially parallel to the longitudinal axis of said tube.

7. The heat exchanger of claim 1 characterized by said preformed steel section having intermediate its flange and that part joined to said cast metal section a substantially radially disposed convolution for expansion and contraction of said tube.

8. The heat exchanger of claim 7 characterized by said flange terminating in a lip disposed substantially parallel to the longitudinal axis of said tube.

9. In a heat exchanger an elongate tube comprising a relatively thick walled section of cast metal with two ends, a section of preformed steel attached to at least one of said two ends of said cast metal section to form said tube, said cast metal section having an external collar adjacent each end thereof for abutting similar collars of adjacent tubes and being adapted to form with said collars of ad jacent tubes a wall near each end of the cast metal sections to protect said preformed steel section from hot gases traversing said heat exchanger, said collars being movable upon one another, said preformed steel section having a substantially outwardly radially extending flange which projects a distance sufficient to abut a corresponding flange of an adjacent tube, said flange being adapted to be joined to the corresponding flange of an adjacent tube along at least a part of its abutting portion.

10. The tube of claim 9 characterized by said preformed steel section being joined to its cast metal section by a molten metal casting around a part of said preformed steel section which extends into said cast metal section.

11. The tube of claim 9 characterized by said flange of said preformed steel section extending radially outwardly a distance equal to substantially that distance which said collars extend.

12. The tube of claim 9 characterized by said flange of said preformed steel section terminating in a lip disposed substantially parallel to the longitudinal axis of its tube.

13. The tube of claim 9 characterized by said preformed steel section having intermediate its flange and that part joined to said cast metal section a substantially radially disposed constriction for expansion and contraction of said tube.

14. The invention of claim 13 characterized by said flange terminating in a lip disposed substantially parallel to the longitudinal axis of said tube.

15. The tube of claim 9 characterized by said preformed steel section having intermediate its flange and that part joined to said cast metal section a substantially radially disposed convolution for expansion and contraction of said tube.

16. The tube of claim 15 characterized by said flange terminating in a lip disposed substantially parallel to the longitudinal axis of said tube.

Belgium Oct. 16, 1951 Germany Sept. 30, 1932 

1. A HEAT EXCHANGER COMPRISING A PLURALITY OF ELONGATE TUBES, EACH TUBE COMPRISING A RELATIVELY THICK WALLED SECTION OF CAST METAL WITH TWO ENDS AND A SECTION OF PREFORMED STEEL ATTACHED TO AT LEAST ONE OF SAID TWO ENDS OF SAID CAST METAL SECTION TO FORM SAID TUBE, SAID CAST METAL SECTION HAVING AN EXTERNAL COLLAR ADJACENT EACH END WHICH ABUTS WITH SIMILAR COLLARS OF ADJACENT TUBES TO FORM WITH SAID COLLARS OF SAID ADJACENT TUBES A WALL NEAR EACH END OF SAID CAST METAL SECTION TO PROTECT SAID PREFORMED STEEL SECTION FROM HOT GASES OF THE EXCHANGER, SAID COLLARS BEING MOVABLE UPON ONE ANOTHER, SAID PREFORMED STEEL SECTION HAVING A SUBSTANTIALLY OUTWARDLY RADIALLY EXTENDING FLANGE WHICH PROJECTS A DISTANCE SUFFICIENT TO ABUT A CORRESPONDING FLANGE OF AN ADJACENT TUBE, SAID FLANGE BEING ADAPTED TO BE JOINED TOGETHER ALONG AT LEAST A PART OF ITS ABUTTING PORTION. 